Project 3 Project Summary Recent evidence suggests that the cancer cells in the primary tumor can precondition distant sites to be maximally receptive for metastasis. However, the mechanisms through which primary tumor cancer cells educate the distant site are not well defined. Exosomes are small microvesicles that are shed from many cells, including cancer cells. We have preliminarily identified that primary tumor PCa cells produce exosomes that can target bone marrow stromal cells (BMSC) and increase expression of pyruvate kinase isoenzyme M2 (PKM2) in the BMSC. PKM2 induces a positive energy balance in cells and promotes production of potential sources of energy that can enrich the local environment. Furthermore, we have found that exosome PKM2 content increases with tumor stage. Accordingly, we hypothesize that primary tumor-derived exosomes alter the metabolic status of the distant bone microenvironment to create a favorable pre-metastatic niche through increasing PKM2 expression in BMSC. To test this hypothesis we will perform the following Aims. Aim 1: Determine changes in exosomes as primary PCa progresses that enable them to create a pre- metastatic niche in bone. Aim 2: Determine the mechanisms through which the exosome-mediated increase of PKM2 in BMSCs create a pre-metastatic niche that promotes metastatic progression. In particular, metabolic changes in the bone microenvironment will be explored Aim 3: Determine prognostic value of PKM2 expression in serum-derived exosomes of PCa patients. When completed, this research will provide both translational and mechanistic insight into how the primary tumor creates a pre-metastatic niche and established the concept that primary tumor-derived exosomes alter the metabolic state of the distant site to favor metastatic growth. Additionally, we will have determined if exosome PKM2 level provides prognostic significance in PCa patients.